300 Win Mag Load Info

[Stats Shooter]

So, I decided to rebarrel my .300 win mag rifle I built. It sits in a Y-Block bedded stock that ways 6 lbs, has timney trigger. The new barrel is a Shilen 30" S8 full bull barrel. I won't get the barrel for another couple months but I am already very excited to begin load development.

The barrel has a 1:10 twist btw.

I want to know if anyone has any velocity data for a barrel of that length? ...Or close to that length. I know that individual results vary, but the only published information I can find uses a 26" or 24" barrel.
My old load used 180 and 200 Grain Accubonds pushed by H1000. I'm going to try and use 220 SMK'S with this newfound barrel length.... Maybe even 240's. Or potentially the new Hornady ELD's.

My reason for the length was to be able to push heavy, high BC, bullets at around 3000-3100 fps. I was getting that kind of velocity using 180's in a 24" barrel with tight groups. But it's throat has eroded and so time to start over.

Thanks

[jmr40]

Until you get the barrel and shoot over a chronograph everything is just a guess. Most published data is from 26" barrels in 300 WM. I'd expect 50-100 fps additional speed from a 30" barrel.

[Stats Shooter]

I know what you mean JMR. The initial research I have done suggest that in the .300wm you add about 25 fps per inch above 26" (up to 30")
The loss gets bigger as you get shorter losing 35 fps/inch going from 26-24..... But you just can't know for sure until you shoot your gun over the chroney.

[Jimro]

My old load used 180 and 200 Grain Accubonds pushed by H1000. I'm going to try and use 220 SMK'S with this newfound barrel length.... Maybe even 240's. Or potentially the new Hornady ELD's.

My reason for the length was to be able to push heavy, high BC, bullets at around 3000-3100 fps.

You should be able to break 3,000 fps with a 190gr SMK using H1000 and a 30" barrel. Possibly, but not likely in my opinion, get to 3,100 fps.

The 220 SMK can probably be pushed between 2,900 and 3,000 safely with that barrel length, as a Mk248 Mod1 load pushes a 220 SMK to 2,850 fps from a 24" barrel, but with a MAP of 68k psi (higher than SAAMI). That same load hovers around 2,900 in a 26" barrel. If you go 25 fps per inches, the additional 6" (or 4") should get you knocking on 3,000 fps if you are willing to go with the 68k psi load. There is no guarantee your barrel will give you 25 fps/inch but it's all academic until you load 'em up and shoot 'em.

If your targets aren't beyond the Transonic Zone in your ballistic path, consider a 208 Amax or Berger 210 VLD. They have a higher BC, but don't particularly handle the transonic zone well which is why they were rejected by NSWC for the new 300 Win Mag sniper load.

If you want a crazy fast load, look at Berger's 168 Hybrid VLD, Hodgdon lists two powders that can push it past 3,100fps from a 24" barrel. It isn't your grandpas 168 SMK, but at the speeds you can launch one from a 30" barrel will give you impressive ballistics out past 1k easily. Heavier options might be the Berger 185 Juggernaught, 200gr 20x bullet, or 215gr Hybrid Target if you are looking to hit with more energy at distance.

I hope this is helpful, or at least food for thought.

Jimro

[Road_Clam]

My go to load for my R700 26" Sondero heavy fluted barrel (also 1-10" twist) is The 208 Amax , 76 gr of H1000. Im at about 2780 fps per my Alpha Crony.

[Stats Shooter]

The 208 A-Max seems to be a popular 300 wm bullet, as does the 215 grain berger. I wonder what the range reports look like on the ELD's from Hornady too. The 225 Hornady ELD has a high BC, .777 for the G1 and .393 G7 I think.

But as of now there just isn't a lot of data on that bullet.

[ShootistPRS]

The ELD bullets are longer for the same weight and if you use solid copper bullets they are longer still. You will have to test your barrel to see what it will stabilize. As to the velocity you can expect remember that there are fast barrels and slow barrels and I have seen 200 fps difference in two "identical" 357 revolvers so you can expect surprises with the new barrel.

[Road_Clam]

I spent a lot of time testing 180, 190 and 200 SMK's and honestly nothing proved to be accurate and consistent. I was getting frustrated with my Sondero barrel. I eventually tried the 208 Amax per the guys over at Snipers Hide, and BOOM I quickly honed in on a real nice .5 MOA @100 yds pet load. I had enough data and confidence in this load to shoot this at the Sig Saur "Reach for a thousand" instructional clinic I took a few years back. My dopes were spot on from 100 to 1000 yds. I do have a good 1 MOA load with the 190 SMK and RL22 but it's not as consistent as the 208 / H1000 load.

[Stats Shooter]

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I spent a lot of time testing 180, 190 and 200 SMK's and honestly nothing proved to be accurate and consistent. I was getting frustrated with my Sondero barrel. I eventually tried the 208 Amax per the guys over at Snipers Hide, and BOOM I quickly honed in on a real nice .5 MOA @100 yds pet load

Same thing happened to me when I first started reloading for this rifle years ago...But it wasn't the bullets, it was Alliance powder..(and the bullets a little bit more on that in a minute).

I tried different bullets, weights, and powder ladders using RE 19 and RE 22... Nothing worked. 3" groups. I was just learning to reload back then, and someone suggested adjusting seating depth. Well that shrunk the groups down to about 1.5 - 1.75" when seated 0.020.

Then I went to hodgdon powders....H1000 and H4831 and every single bullet type and weight grouped near MOA or better. My best loads though we're using 180 or 200 Grain nosler Accubonds. 1/4 moa easy.

I do not use alliant powders anymore. They seem to get great velocity, but they are too temp sensitive and the SD on the velocity is too high.

[Jimro]

I've found that there aren't really "bad powders" so much as powders that aren't suitable to a given load in a given cartridge. I never could get Varget to group as tight as IMR4064 in multiple 308 Win rifles, although Varget is supposedly a very good powder for match grade 308 I found that IMR4064 was better for me and the small sample of rifles I have.

So, Alliant powders are fine, but they I agree aren't the best in 300 Win Mag. Reloader 22 is great in 6.5x55 where it keeps pressures down, and RL19 is ok in 30-06 within normal velocity range. The 300 Win Mag is just better with different powders.

H1000 has been the "go to" powder for 300 Win Mag with heavy bullets for a few years now, as it performs very well at 60k psi and higher burn rates. I'm not sure it would do as good as Re22 in a 6.5x55 where the pressures are significantly lower.

Not to be argumentative, just hopefully adding some context.

Jimro

[Stats Shooter]

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Not to be argumentative, just hopefully adding some context.

That's not being argumentative, that's just a fact. My brothers .375 HH hunting rifle is very accurate. He uses Speer 270 gr BT spire points and RE15. Now, he doesn't go out and shoot it a lot on hot days, but every fall before elk season he shoots 12-15 rounds at different distances to make sure his scope is on, and to refamiliarize himself with his rifle, but in his case re powder is great.

I have the same problem getting CFE 223 to shoot accurately. I get great velocity using CFE in both .308 and 556, but I can't get it to group well in my guns with the bullets I have tried.